Using Unix in a Networked Environment

• Workstation fundamentals
• Architecture of Unix
• Unix files and commands
• X Window System
• Unix utilities -- advanced use

Abrahams, Paul W., and Bruce A. Larson,

Unix for the Impatient,

Reading, MA: Addison-Wesley Publishing Company 1996.

ISBN: 0-201-82376-4.

Hahn, Harley,

A Student's Guide to Unix,

New York: McGraw Hill, 1996.

ISBN: 0-07-025492-3.

Nemeth, system administration,

On-line manual pages

Window-oriented manual collection

Book Reader, Answer Book, Info, etc.

Command interpreters

C shell

Bourne shell

Files and directory manipulation

cd

mkdir

mv

cp

ls

Text editing

vi

emacs

pico

Mail

Mail

mail

pine

Software development

cc

lint

make

Nifty utilities

egrep

find

awk

sed

Graphic applications

X window system

Networking

rlogin

ftp

archie

netscape

File Services

Directories

Unstructured files

Devices

Mounting disks

Job control

Creation and termination

Memory management

Interprocess communication

Network services

Internet connectivity

Protocols

Networked file systems

AIX --	IBM
A/UX --	Apple
IRIX --	Silicon Graphics
HP/UX --	Hewlett-Packard
NextStep --	Next, Inc.
Open Desktop --	Santa Cruz Operation
OSF/1 --	Open Software Foundation
Solaris --	SunSoft
SunOS --	SunSoft
UnixWare --	Novell
Digital Unix --	DEC

NOT "real" UNIX
Windows NT
OS/2
Open VMS

If it satisfies Spec 1170,

it can be called Unix.

X/Open

Consortium of major Unix vendors and user organization

Controller of Spec 1170

Owner of the Unix trademark

Widgets and style

"look and feel"

3-D look derived from

Microsoft Presentation Manager

Microsoft Windows

COSE

Common Desktop Environment

Supported by

HP

IBM

Santa Cruz Operation

Sun Microsystems

Novell

Digital

...

Window manager

Motif with some support for OpenLook

Front panel

Based on HP's Visual User Environment

Application Help system

Based on SGML - Standard Generalized Markup Language

Support of present man pages

Personal productivity tools

Mailer

Text editor

etc.

• Connects shell to your home directory
• Directs standard I/O to/from terminal
• Defines initial environment variables
• Starts shell process owned by you

And...

in the X-Window System does a lot more

Upper and lower case matter!

A ROSE is not a Rose is not a rose.

To change

passwd

Encrypted and usually stored in /etc/passwd or /etc/shadow

• restrictions on number of characters

• do mix upper and lower case
• do use two words together or put a number in a word
• use first letters of words in a phrase (uflowiap)

• don't use a single word
• don't use something guessable e.g. spouse, children, pets, car, movie, computer, your login name
• don't tell anyone

date

Show date and time

cal mm yyyy

Display calendar

hostname

Display name of workstation

whoami

Display your login name

echo "hi there"

Echo message to screen

uptime

Display current system status

uname

Displays name of current Unix system

command options files [RETURN]

separated by white space (spaces, tabs)

command

Required

Program to be executed

Executable file must be in your path

options

Optional

Modify the command

May have their own arguments

Similar to / in MS-DOS commands

• -l
• -id
• -5
• +5
• -o outfile

files

Usually one

Generally specifies input to the program

man command

Display online manual pages for command

man ls

Display online manual page for ls

man -k keyword

Use keyword to find manual page

apropos keyword

Same as man -k keyword

whatis command

Display one line summary for command

man 2 kill

Prints manual page for system call kill

whereis command

To find section of man page for command

• Pathname
  • Series of components separated by " / ".
  • /var/dss/namedb/src/passwd
• Few restrictions
  • Components
    • Up to 256 characters in length Your mileage may vary.
    • Can use letters, numbers, periods, underscores, hyphens
    • Avoid other punctuation, spaces, control character
  • Pathnames
    • Up to 1024 characters in length
  • No
    • no device specifiers (a:, b:)
      a:\autoexec.bat
    • no special restrictions on "."
      /tmp/thisisok
      /tmp/and.so.is.this

Current directory

Each process is connected to a directory

Absolute pathnames

Start with "/"

Relative pathnames

Don't start with "/" .. and .

..

Refers up the tree to parent directory

.

Stays still

cd

Change directory to home directory

cd path

Change directory

pwd

Print working directory

mkdir newdir

Make a directory

rmdir olddir

Remove an empty directory

ls

List files in current directory

ls /usr/users/curry

List files in a particular directory

ls -l

List files in long format

ls -a

List all files, including hidden ones

ls -F

List files, indicating file types (* = executable, / = directory)

ls -R /etc

List files recursively starting with /etc

ls -alR /

List all files for a very, very long time

Type man ls for many more options!

cp from to

Copy a file

(Can use wildcards * and ?)

mv from to

Move a file

rm filename

Remove (unlink) file

There is no undelete!

touch filename

Create empty file, or update access times if file exists

more filename

Display a file in screen-size pages

cat filename

Display file on screen without pause

cat filename1 filename2

Concatenates files and displays on screen

lpr filename

Print file

diff filename1 filename2

Compare two files

head filename

Show first 10 lines of file

tail filename

Show last 10 lines of file

grep string filename

Search for a string within file

wc filename

Count lines (-l), words (-w), and characters (-c)

ln -s pathname nickname

Give a file or directory another name

file filename

Guess contents of file

sort filename

Displays sorted file

uniq filename

Removes repeated lines in file

rev filename

Reverses order of characters on each line

spell filename

Reports misspelled words in file

cmp filename1 filename2

Compares two files

script filename

Saves record of actions to file

many to one

tar cvf save.tar ./nsf

Places file(s) of directory nsf into single file save.tar

one to many

tar xvf save.tar

Extracts from tar file

bigger to smaller

compress save.tar

Creates compressed file save.tar.Z

gzip save.tar

Creates save.tar.gz

smaller to bigger

uncompress save.tar.Z

gunzip save.tar.gz

Restores save.tar

The id is the basis of all protection in Unix.

Users and groups are known by numbers.

In most versions of Unix,
a user may be in several groups.

Two associations for a file

owner (user)

group

Three types of file accessors

same user

same group

others

Three types of file access

Read Write eXecute

For directories,

Read = list names of files in directory

Write = add, remove files from directory

Execute = access files within the directory

% ls -l
total 1550
-rw-r--r--  1 stigle  16802 Jan 20 17:07 book.reviews
-rwxr-xr-x  1 stigle    331 Feb 16 09:39 bx
drw-r--r--  1 stigle    512 Feb 11 10:12 cartoons
-rw-r-----  1 stigle  29521 Jun  9  1993 email.guide
-rw-------  1 stigle   1366 Feb  8 13:57 forms
-rw-rw----  1 stigle   1418 Jan 24 11:41 forweb
-rw-r--r--  1 stigle  25147 Jan 25 16:07 ftp.faq
drw-------  1 stigle    512 Jan 15 13:16 gopher

chmod g+w filename

Let group members write the file

chmod o-r filename

Make file unreadable by others

chmod ugo+r filename

Make file readable by everyone

chmod people+access filename
chmod people-access filename

Add or subtract permissions for file

chmod people=access filename

Set permissions for file

chgrp group filename

Set group id of a file

One anachronism

Sticky bit

As presented by ls

-rwsr-xr-x 1 brock system

Executes with the power of user brock User brock may also execute the file

-rwxr-sr-x 1 brock uncaww

Executes with the power of group uncaww

drwxrwxrwt 1 brock system

A sticky-bit directory

Any user can creates files here, but you can only delete your own files.

Testing your octal

lpr filename

Prints file to line printer.
Don't print PostScript to an ASCII printer!

lpr -Pprinter filename

Prints to specified printer

lpr -#2 filename

Prints 2 copies

lpq -Pprinter

Displays spooled print jobs

lprm -Pprinter job#

Removes job from print queue

Related System V commands

• lp
• lpstat
• cancel

• "network-transparent windowing system"
• "bringing coherence to the [UNIX] marketplace"

• Window manager
  • Controls windows
    • Size and placement
    • Iconified or displayed
  • Frames windows
    • 3-D bevelled look
  • Provides "buttons" in frames
  • Destroys windows
    • If absolutely necessary
  • dtwm, in CDE
• Session manager
  • Controls "login"session
  • Starts clients
  • Can "save" sessions
  • dtsession, in CDE

• history
• redirection and piping
• globbing -- matching
• job control
• aliasing
• scripts

Varies wildly on different versions of Unix!
This is for the C-shell under Digital Unix V3.2C.

To complete file names

• set filec
  • Best set in .login
• Type some stuff.
• Press ESC ESC.
  • If unique, completes word.
  • If not unique, beeps.
• Press ^D
  • Shell gives a list of possible completions.

Cut-and-paste

Standard I/O

standard input

keyboard

standard output

terminal screen

standard error

terminal screen

Rediretion

One of the concepts from Unix.

Partially borrowed by MS/DOS. Too bad they couldn't do it right.

operator	action
com1 | com2	Connect the standard output of com1 to the standard input of com2.
com1 |& com2	Connect the standard output and standard error of com1 to the standard input of com2.

Unix application philosophy

Design small utilities that make interesting transformations of input to output.

Provide a way to connect these utilities.

Frequently used with ls, cd, cp, etc.

pattern	match
*	Matches zero or more characters
?	Matches one character
[ch]	Matches characters 'c' or 'h'
[A-Z]	Matches any upper case letter
X{a,15}	Matches strings "Xa" and "X15"
~brock	Expands to brock's home directory
~	Matches your home directory

Examples

ls *.c

Lists all C files within current directory.

ls /users/*/X?[A-Z0-9iou]*

Looks rather useless.

Unix gurus call the use of *, "globbing".

To prevent the C shell from processing special characters, quote the characters.

quoting	action
\c	Quote single character c which follows backslash.
'string'	Quote all characters between the signel quotes except for !
"string"	Quote all characters between double quotes except $, `, !, \, and [CR]. Allows variable, command, and history substitution
set noglob	Command to shut off globbing.
unset noglob	Turn globbing back on.

• For MS-DOS users
  • alias copy cp
  • alias dir ls
  • alias delete rm
  • alias type more
• For typos
  • alias loogut logout
  • alias mroe more
• For help
  • alias help man
• To shorten command names
  • alias h history
  • alias g gnuemacs
  • alias e emacs
  • alias gmake /usr/local/hacks/bin/gnumake
• To store options for commands
  • alias ll 'ls -l'
  • alias mag 'magic -d X11'
  • alias report 'nroff -ms rep.fil'
  • alias cd 'chdir \!*;set prompt="`pwd`>"'
  • alias laser 'lpr -Prbh221'

To list current aliases

alias

To remove an alias

unalias aliasname

Aliases disappear when the shell is closed! To save an alias, put it in the shell initialization file.

Passed by shell to programs you execute.

printenv

Lists environment variables in the C shell.

printenv VARIABLE

Lists value of a single variable.

setenv VARIABLE value

Set or change environment value.

unsetenv VARIABLE

Remove variable.

man program

Find which environment variables a program uses

set

List values of all current variables.

echo $var

Display value of a single variable.

set var = value

Set or change the value of variable.

set var

Turn on a toggle variable.

unset var

Undefine a variable.

set var = `command`

Set variable to value printed to standard output by executing a command.

• On login, C shell reads:
  • .cshrc
  • .login
• On logout, C shell reads:
  • .logout
• Non-login C shell reads
  • .cshrc

C shell files can

• set C shell variables
• set environment variables
• execute commands
• define aliases

To test an initialization file type "source pathname".

Frequent, repetitive, and boring tasks should be done with shell scripts.

Format of the shell script

C shell

#! /usr/bin/csh -f
commands...
#comments

Bourne shell

#! /bin/sh
commands...

PERL

#! /usr/local/bin/perl
neat PERL stuff

After saving a shell script make it executable by typing "chmod ugo+x script".

Nothing interesting ....

#! /usr/bin/csh -f
# hello world script
echo "Hello world\!"

Reading command line arguments

#! /usr/bin/csh -f
# Print GIF file to PostScript printer
giftopnm ${1} \
     | pnmtops -center -scale 2 \
     | ps -Prbh013

A little testing

#! /usr/bin/csh -f
if ( -f userids ) then
     grep ${1} userids
else
     echo "file userids is missing"
endif

#! /bin/csh -f
# calculate square root
if ( ${#argv} < 1 ) then
  /usr/bin/echo "You forgot the number:  \c" 
  set num = "$<"
else
  set num  = "${argv[1]}"
endif
set numok = `expr "${num}" : '^[ ]*[0-9][0-9]*[ ]*$'`
if ( ! ${numok} ) then
  echo "Can't compute the sqrt of ${num}\!"
  exit 1
endif
@ num = ${num}
@ sqrt =  0
while ( (${sqrt} + 1) * (${sqrt} + 1) <= ${num} )
  @ sqrt = ${sqrt} + 1
end
echo "floor(sqrt(${num})) = ${sqrt}"
exit 0

cut

Extracts fields and characters from lines of input files
finger | cut -c10-35
Displays the "full name" of users.

tr

Copies standard input to standard output while it translates characters
tr A-Z a-z < lorentz.tex
Displays a file in lower case

sed and awk

Very powerful string processors
sed -e "s/HOST/$host/g"
Replaces HOST with the host name

head

Prints the first lines of a file
man sed | head -20
Displays the first twenty lines of a man page

tail

Prints the last files of a file
man sed | tail -20
Displays the last twenty lines of a man page
finger | tail +2 | cut -c10-35
Really displays the "full name"

dirname

Finds the directory part of a pathname
dirname /tmp/myprog.c
Returns "/tmp"

basename

Removes the directory part of a pathname along with unwanted suffixes basename /tmp/myprog.c .c
Returns "myprog"

expr

Arithmetic expression evaluation and regular expression matching
expr " 0# A" : '.*\([A-Za-z]\).*'
Returns "A"

uname

Displays type of Unix system

hostname

Displays name of host

getopts

For sophisticated processing of options given as arguments to the script. Read the man page!

Command format

• find directory searchcriteria

Simple example

find . -type f -size +200 -print

To display names of all files in current directory and all subdirectories larger than 102,400 characters (200 blocks).

Some find tests

Find directories in /tmp accessed this week

find /tmp -type d -atime -7 -print

Remove backup files created by emacs

find . -type f -name "*~" -exec rm {} \;

Find large files no one is using

find . -type f -size +500 -atime +30 -print

Find files and directories writable by everyone

find . -perm -002 -print

Usual logical operators

and

case1 case2

or

case1 -o case2

not

\! case

grouping

\( case \)

Highfalutin examples

Invented by linguists and mathematicians. Beloved by computer scientists, particularly the theoretic ones

A way to specify searches such as "Match a string that consists of a bunch of a's followed by either iou or IOU.

Regular expressions are used in

• text editors -- ed, vi, emacs
• parsers for compilers -- lex
• search programs -- egrep, archie

Command format

• egrep regexp files...

Example atomic elements

a

Matches character "a"

.

Matches any single character

[iou]

Matches any of three characters

[0-9]

Matches any digit

^

Matches beginning of line

$

Matches end of line

Example regular-expression operators

(na)*

Matches zero or more consecutive occurrences of "na"

X|Z

Matches "X" or "Z"

s?

Matches an optional "s"

Examples to ponder

• egrep 'potatoe? chip' files
• egrep '^ba(na)*$' files
• egrep 'cat|dog' files